Remote-controlled unmanned aerial vehicles have become inexpensive and now represent a potential security threat to both government, corporate, and private facilities. For example, a large variety of remote-controlled quadracopters (aerial vehicles with four sets of rotor wings, which are inherently stable and easy to fly) have become available on the hobby market in recent years. Quadracopters available for the hobby market range from inexpensive unit such as the UDI U818A quadracopter with on-board remote-viewable low-definition video, to units in the $3000 price range such as the XP2 Quadracopter by XProHeli, which includes a gimbaled video camera which transmits live high-definition video images back to the remote control unit. Many units are made to be controlled via standard IEEE 802.11b wireless Ethernet, so they can be controlled by using a smartphone as the remote control and video viewing unit. Recently, self-navigating quadracopters have become available which can be programmed to fly a course defined by a series of waypoints defined by GPS coordinates.
While remote-controlled aerial vehicles are fun toys for hobbyists, they may also be used by criminals, for instance to spy through windows, to spy inside a fenced secure perimeter, or to smuggle contraband such as a cell phone or a weapon or an explosive over the security wall and/or fence of a secure facility such as a prison. There is a need for innovative technologies which can detect UAVs near or within a secure perimeter. There is a further need for innovative technologies which can detect remote-control devices used to control a UAV within or near a secure perimeter. There is a further need for innovative technologies which can disable a UAV detected within or near a secure perimeter. With regard to the problem of airborne smuggling of contraband into prisons and the like, there is a further need for innovative technologies which will facilitate automated detection of contraband that may be lobbed over a prison wall, or dropped from a UAV or private plane at significant altitude.
Techniques are known in the art for detecting electronic devices through radiated or re-radiated energy. Such techniques are described in US patent application #20090135046 (hereinafter Steele) and US patent application #20060082488 (hereinafter Keller) however, the ability to locate a target accurately in space using a directional receiver typically requires a large directional antenna (such as a parabolic RADAR dish, or a large phased array of antennas). Such techniques are not suitable for use in an urban area unless they can be highly targeted, and are only targeted at real threats. There is a need for innovative location technologies that will allow equipment that can be unobtrusively installed at a small facility (such as a private home) to accurately locate potential UAV threats. There is a need for more accurate location technologies, suitable for verifying real electronic device threats in a crowded urban environment.
Techniques are known in the art for directing energy toward a potential threat such as a UAV. Keller discloses a method of disabling electronic components with a high-powered burst of electromagnetic radiation. US patent application #20110120335 (hereinafter Fullerton) discloses a method of disabling a target by focusing very loud sound waves (formed through a timed array of detonations). US patent application #20090288573 (hereinafter Rotkopf) discloses a method for disabling an aerial target such as a low-velocity rocket, using explosively formed blade projectiles fired from an intercepting rocket. While each of these techniques have applications in urban warfare, these techniques have the potential to cause collateral damage in a peace-time suburban or urban setting. There is a need for innovative technologies to disable slow-moving UAVs such as those sold on today's hobby market, without the potential for causing collateral damage to persons or structures in a suburban or urban environment.
When locating sources of electromagnetic radio frequency (RF) radiation (whether such radiation is primary emitted radiation such as might be emitted from a video-camera-equipped UAV) or primary reflected RF energy such as would be detected by conventional RADAR, or harmonic or cross-product RF emissions created by nonlinear circuit elements when illuminated by a probe signal such as a RADAR signal, it is imperative to be able to locate the source of such RF accurately enough to do something useful (such as disable a UAV emitting such RF radiation).
In a RADAR system, a highly directed beam of energy is emitted either from a shaped single antenna (such as a parabolic dish) which is pointed in a given direction, or from a phased array of antennas, whose transmitted energy sums in a given direction. The time between when transmitted energy goes out and when reflected energy returns gives the distance to the reflecting object, and the angle of the antenna gives the direction. Thus the precision to which an object can be located in space by a RADAR system depends on the precision of the time from RF broadcast to RF reception, and on the angular directivity of the antenna. Angular directivity may be thought of as related to antenna gain, which is the ratio of the highest sensitivity direction of reception of an antenna to the average sensitivity of reception (averaged over all possible directions) of that antenna. Antenna gain scales with the size of an antenna array (or with the size of a shaped antenna such as a dish) compared to the wavelength of the RF frequency being received/transmitted.
A shaped antenna is often far less expensive than an antenna array of equivalent antenna gain, but if a shaped antenna is to be used to locate objects throughout a volume of space, it must be continually moved in a repetitive pattern (for instance rotated in a circle), and the mechanism to do the repetitive movement may itself be expensive and unreliable compared to the electronics needed to drive an array of fixed-position antennas. There is a need for innovative technologies that allow accurate location of UAVs near a facility with minimal cost for the electronics and hardware involved.
Methods known in the art for disabling or destroying aerial targets in warfare (both battlefield warfare and urban warfare) usually use explosively propelled projectiles (such as disclosed by Rotkopf), or bursts of high-powered electromagnetic energy (such as disclosed by Keller), or extremely loud sounds produced by timed detonations (such as disclosed by Fullerton), however, these methods all have the potential to cause undesirable damage should they be used in peacetime in an urban or suburban environment. There is a need for innovative technologies capable of disabling a UAV without causing collateral damage in an urban or suburban environment. Furthermore, there is a need for innovative technologies for detecting and destroying or disabling UAVs at short range.